In my prior U.S. Pat. Nos. 3,580,112 and 3,593,599 I have disclosed a transmission system of this general type wherein several forward speed ratios (conventionally referred to as first, second and third gear) and a reverse speed ratio of the output shaft, with reference to the engine, can be brought about under the control of a manually settable speed selector and switchover means controlled thereby, the speed selector having several forward positions (not all of them being of interest here) and a reverse position. In a forward position, switching between low ("first gear"), intermediate ("second gear") and high ("third gear") forward speed ratios takes place automatically in response to changes in the position of an accelerator pedal, giving rise to a load-dependent fluid pressure, as well as in the speed of the output shaft which is sensed by another fluid-pressure generator. Via a conventional planetary-gear train, shifting from first through second to third gear and vice versa is effected with the aid of several clutches and brakes (collectively termed "drive-establishing means"), one such clutch being actuated in both third gear and reverse. A damper associated with a control valve for this clutch serves to retard full operation thereof by a substantially invariable delay period, as disclosed in the second one of my above-identified prior patents, in order to insure a smooth cut-in. This is accomplished by subjected the damper to a load-dependent fluid pressure balancing load-dependent variations in the supply pressure under which fluid is admitted to the clutch via the control valve in the off-normal position of two cascaded shift valves, a feedback connection from the clutch to the cylinder of the control valve tending to displace the piston thereof against a biasing force from a normal position into a throttling position upon partial pressurization of the clutch. The associated damper comprises a plunger mechanically linked with this piston, the plunger responding to further pressurization of the clutch by restoring the piston to its normal position in which fluid from the high-pressure supply is rapidly admitted to the clutch to complete its operation.
Such an arrangement, which retards full clutch operation by a substantially constant delay period, is advantageous in that it makes the cut-in time virtually independent of changes in the supply pressure while letting the final clutch pressure vary with load. A drawback, however, resides in the fact that the same delay period intervenes upon upshifting to third gear and upon shifting into reverse, the latter operation occurring generally on standstill or at very low speeds making such a delay unnecessary and wasteful in terms of excessive wear of the friction layers of the clutch.